This invention relates to an apparatus and method for monitoring the power of a device under test (DUT). More particularly, the invention relates to an apparatus and method in which the power of a semiconductor device under test is monitored without reliance on dedicated current and voltage monitoring signals available from a semiconductor test unit.
The above identified, commonly owned U.S. application Ser. No. 352,760 relates to a technique for monitoring the current and voltage of a device in order to determine the power consumption of that device. The calculated power consumption is then used to thermally condition the device, for example, to maintain the temperature of the device at or near a constant set point. While having more general applicability, such technique may advantageously be utilized in connection with performance testing of semiconductor devices, such as memory devices or microprocessors.
Performance testing is typically accomplished by connecting the semiconductor device to a load board of a test device, which then performs various testing on the semiconductor device. For example, the test device may measure the maximum operating frequency of the semiconductor device. It is known, however, that devices under test (DUTs) self-heat, and that the resulting rise in temperature may cause the performance of the DUT to degrade. This may cause under-reporting of the performance of the DUT. Various temperature forcing techniques may be used to attempt to maintain the temperature of the DUT around a constant set-point. However, with many current semiconductor devices, instantaneous power fluctuations may be so severe and dramatic, that current temperature forcing systems often fail to accurately offset effects of self-heating.
The power monitoring technique of application Ser. No. 352,760 involves measuring instantaneous power fluctuations in order to predict changes in self-heating before they occur. Measured power fluctuation is utilized to control a temperature forcing system in order to offset self-heating to maintain a DUT at a constant set point. This technique may use signals from the test units power supply to determine the power being supplied to the DUT. There are currently, however, various types of test units are now available which vary in design. Many test units do not provide output terminals to provide power supply monitoring signals, and in many cases, the power supply is not readily accessible. Further, it is necessary to avoid interruption of the power supply in any way that would interfere with or degrade the characteristics of the power signals to the DUT. Thus, there is a need for a technique to measure the voltage and current utilized by a DUT in a way that avoids adverse effects on the power supplied to the DUT.
In accordance with an embodiment of the present invention, a device provides active monitoring of power of an electronic device, such as a semiconductor device under test. The device according to the invention, includes at least one magneto-resistive current sensor provided external to the device and a power source. The current sensor detects current to the device and provides a detection signal proportional to the current drawn by the device from the power source. A monitoring circuit receives as input the detection signal from the magneto-resistive current sensor and a signal representative of voltage supplied to the device from the power source, and multiplies those signals to obtain a signal representative of the power of the device.
In accordance with another embodiment of the invention, a method of detecting the power of an electrical device, such as a semiconductor device under test, includes detecting current drawn by the device from a power source with at least one magneto-resistive current sensor provided external to the device and the power source. The current sensor detects current to the device and provides a detection signal proportional to the current drawn by the device from the power source. Instantaneous power of the device is calculated based on the detection signal from the magneto-resistive current sensor and a signal representative of voltage supplied to the device from the power source.
In accordance with another embodiment of the invention, a system controls the temperature of an electronic device. The system includes an active power measuring circuit comprised of at least one magneto-resistive current sensor provided external to, and in between the electronic device and a power source. The current sensor provides a detection signal that is proportional to the current drawn by the electronic device from the power source. The detection signal is multiplied by a signal representative of voltage supplied to the electronic device from the power source to obtain a signal representative of the power of the electronic device. A heat exchanger regulates the temperature of the electronic device in response to a control circuit that adjusts the heat exchanger based on the detected power consumption of the device.
According to one aspect of the invention, the power source and the current sensor(s) are located on a common board (e.g., the load board) of a semiconductor test unit. Alternatively, the current sensor(s) is (are) located on a separate board separate board, between the power supply to the device and the device itself. The monitoring circuit is provided on a printed circuit board which is connected to the load board by an interface cable, which transmits signals from the at least one current sensor.
According to another aspect of the invention, a plurality of current sensors are arranged in parallel to thereby divide the current supplied from the power supply to the electronic device, wherein each current sensor outputs a corresponding detection signal proportional to detected current. The monitoring circuit sums each output from the plurality of current sensors to obtain a signal corresponding to the total current drawn by the electronic device.
According to another aspect of the invention, the monitoring circuit includes an isolation amplifier that provides an isolated signal based on the signal representative of the voltage supplied to the electronic device from the power source. The isolated signal is multiplied by a signal corresponding to total current drawn by the electronic device as detected by the at least one current sensor.
According to another aspect of the invention, the signal representative of the power of the electronic device is provided to a thermal control circuit that controls the temperature of the electronic device. The thermal control circuit controls a heat exchanger that selectively heats or cools the electronic device in response to detected power drawn by the electronic device to maintain the device near a constant set point.
According to another aspect of the invention, the heat exchanger is comprised of an active, conductive heater.